An electric motor converts electricity into mechanical power in the form of a rotating shaft known as a rotor. The angular velocity of the rotor may be based on the electricity flowing through field windings in the stator of the electric motor. A controller device may implement a method known as field-oriented control (FOC), also known as vector control, to determine the amplitude of the electrical current that should flow through each field winding of the stator.
A controller device using FOC may measure or estimate the electrical currents through the field windings and determine the desired electrical currents to flow through the field windings. The controller device may include one or more feedback loops designed to regulate the electrical currents to their desired levels. A controller device that implements sensorless FOC may also include circuitry configured to estimate the angular velocity of the rotor. The controller device may compare the estimated angular velocity to the desired angular velocity to determine an error signal for the angular velocity. To correct the angular velocity to the desired angular velocity, the controller device may control the electrical currents through the field windings based on the error signal for the angular velocity.
Rotor lock is a condition in which the rotor of an electric motor is partially or fully obstructed. Many different events may cause rotor lock, depending on the environment of the electric motor. For example, an object may enter the electric motor and contact the rotor, causing rotor lock. In another example, an internal component of the electric motor may malfunction or dislodge, causing rotor lock. In some examples, the rotor may have nonzero angular velocity during rotor lock, such as when the rotor is partially obstructed.